Beta-ketothiolase deficiency | |
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Other names | 3-oxothiolase deficiency, Mitochondrial acetoacetyl-coenzyme A thiolase deficiency, Alpha-methyl-acetoacetyl-CoA thiolase deficiency |
Isoleucine |
Beta-ketothiolase deficiency is a rare, autosomal recessive metabolic disorder in which the body cannot properly process the amino acid isoleucine or the products of lipid breakdown. [1] [2] Along with SCOT deficiency, it belongs to a group of disorders called ketone utilisation disorders.
The typical age of onset for this disorder is between 6 months and 24 months.
The signs and symptoms of beta-ketothiolase deficiency include vomiting, dehydration, trouble breathing, extreme tiredness, and occasionally convulsions. These episodes are called ketoacidotic attacks and can sometimes lead to coma. Attacks occur when compounds called organic acids (which are formed as products of amino acid and fat breakdown) build up to toxic levels in the blood. These attacks are often triggered by an infection, fasting (not eating), or in some cases, other types of stress.[ citation needed ]
This condition is inherited in an autosomal recessive pattern and is extremely rare having only been reported in 50 to 60 individuals throughout the world.[ citation needed ]
Mutations in the ACAT1 gene cause beta-ketothiolase deficiency. The enzyme made by the ACAT1 gene plays an essential role in breaking down proteins and fats in the diet. Specifically, the enzyme is responsible for processing isoleucine, an amino acid that is part of many proteins. This enzyme also processes ketones, which are produced during the breakdown of fats. If a mutation in the ACAT1 gene reduces or eliminates the activity of this enzyme, the body is unable to process isoleucine and ketones properly. As a result, harmful compounds can build up and cause the blood to become too acidic (ketoacidosis), which impairs tissue function, especially in the central nervous system.[ citation needed ]
In beta-ketothiolase deficiency, alpha-methyl-beta-keto-butyrate, alpha-methyl-beta-OH-butyrate and tiglyl glycine (upstream metabolites of the affected enzyme) may accumulate and may be detected on urine organic acid analysis by GC-MS. This may aid in the diagnosis, but for a more definitive diagnosis genetic confirmation needs to be done.[ citation needed ]
During a ketoacidotic crisis, intravenous fluids with glucose and electrolytes should be administered immediately. Bicarbonate (initially as 1 mmol/kg over 10 minutes followed by continuous infusion) should be given to treat acidosis. Carnitine supplementation may be helpful. Dialysis is effective but usually not necessary. Unconscious patients and those with severe dyspnea may require mechanical ventilation. Long-term management involves avoidance of fasting (and intravenous glucose in cases of fever or vomiting) and, in children, a mildly restricted protein intake (1.5-2g/kg/day), avoidance of fat-rich (ketogenic) diet, and L-carnitine therapy in those with low carnitine levels. Avoidance of isoleucine overload might prevent neurological complications, but currently there is no evidence to support this[ citation needed ]
Propionic acidemia, also known as propionic aciduria or propionyl-CoA carboxylase deficiency, is a rare autosomal recessive metabolic disorder, classified as a branched-chain organic acidemia.
Isovaleric acidemia is a rare autosomal recessive metabolic disorder which disrupts or prevents normal metabolism of the branched-chain amino acid leucine. It is a classical type of organic acidemia.
Maple syrup urine disease (MSUD) is a rare, inherited metabolic disorder that affects the body’s ability to metabolize amino acids due to a deficiency in the activity of the branched-chain alpha-ketoacid dehydrogenase (BCKAD) complex. It particularly affects the metabolism of amino acids- leucine, isoleucine, and valine. With MSUD, the body is not able to properly break down these amino acids, therefore leading to the amino acids to build up in urine and become toxic. The condition gets its name from the distinctive sweet odor of affected infants' urine and earwax due to the buildup of these amino acids.
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Mitochondrial trifunctional protein deficiency is an autosomal recessive fatty acid oxidation disorder that prevents the body from converting certain fats to energy, particularly during periods without food. People with this disorder have inadequate levels of an enzyme that breaks down a certain group of fats called long-chain fatty acids.
Biotinidase deficiency is an autosomal recessive metabolic disorder in which biotin is not released from proteins in the diet during digestion or from normal protein turnover in the cell. This situation results in biotin deficiency.
Glutaric acidemia type 2 is an autosomal recessive metabolic disorder that is characterised by defects in the ability of the body to use proteins and fats for energy. Incompletely processed proteins and fats can build up, leading to a dangerous chemical imbalance called acidosis. It is a metabolic myopathy, categorized under fatty acid metabolism disorder as that is the bioenergetic system that it affects the most. It also affects choline metabolism.
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A broad classification for genetic disorders that result from an inability of the body to produce or utilize an enzyme or transport protein that is required to oxidize fatty acids. They are an inborn error of lipid metabolism, and when it affects the muscles also a metabolic myopathy.
Citrullinemia type I (CTLN1), also known as arginosuccinate synthetase deficiency, is a rare disease caused by a deficiency in argininosuccinate synthetase, an enzyme involved in excreting excess nitrogen from the body. There are mild and severe forms of the disease, which is one of the urea cycle disorders.
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